Nutrient lockout or Calcium deficiency?

A question of a fellow grower:

  • Strain: Unknown.

  • Type (fem/auto/reg): regular

  • Climate (indoor/outdoor): indoor tent 70x70x160

  • Medium (soil/hydro/details): premium potting mix with included nutrients and I added about 1/5 perlite. I also flushed the potting mix before planting

  • pH of runoff: 6.2

  • Nutrient mix strength (EC/TDS): unknown

  • Light type & schedule: MarsHydro LED 300w and a 240w. 12/12. I skipped the vegetative stage

  • Temperatures day & night: daytime temps in spring here are up to 38’C /100’F and will get to about 44’C / 110’F in summer. Night time temps vary greatly ranging between 15’C / 60’F up to about 28’C /82’F

  • Humidity day & night: between 10 - 20% most days but I place a wet rag near the air intake to try keep the humidity up over 35%. Unless it rains, which only happens about 10 days a year if we’re lucky. Night time can get to around 70%

  • Ventilation: 100mm intake fan with two USB fans inside

  • AC: NA

  • Humidifier: NA

  • De-humidifier: NA

  • Co2:NA

I have treated this as a Ca deficiency by giving the plant a couple of good flushes then adding Ca to the soil. I raised my lights too just in case it was light burn. The browning which started from the centre at the base of the top leaves moving out towards the tips and even after treatment, continued down to the next node. It now appears to have stopped as the new growth looks healthy. I’m not sure if this was a nutrient lockout or Calcium deficiency which was fixed by the flushing or the added Ca. Any advice you can give would be appreciated.

Your pH is at 6.2. That is low for soil.

Try to get your runoff pH up to 6.5-ish. That looks like a micronutrient lockout, for sure.

I forgot to mention that the tap water has a Ph of 7.2 and with no added nutrients, the runoff drops to 6.2. Would you recommend to continue flushing?

You need to start adjusting your tap water before watering your plants.

So, lower the tap water to 6.5 and flush until the runoff is the same yeah?

So, if your tap pH is 7.2 but your run-off is 6.2, that means your soil is slightly acidic. Since you’re already regularly watering with 7.2 water, and your soil is getting so acidic, I’d say a flush would definitely be more effective than trying to raise or lower through regular watering/nutes. I think a true flush would work well. It’ll probably take a good half hour to do & can be a huge mess, but your plants will love you for it.

Since your plant is so young, you’ll want to be careful. Definitely get your fans ready, b/c you’ll want to assist the pot in drying out, as much as possibly. Note: down not direct the fans at the plant, itself, though. I have flushed auto seedlings without any trouble, so your baby should be fine.

There are more knowledgeable people around here who might have other advice, too.

Hey, @raustin, what do you think?

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Once the flush is done, make sure you adjust your pH, every time. :grinning:

Hmm, I’ve never flushed a plant that small in such a big pot. I mean, it can be done, but be careful.

Last grow, I flushed my 2-3 week old autos without any issue. Well, Tangie lost a little time, but she was noted by the breeders to be very sensitive.

What would you recommend, @raustin? Just watering with a water pH’d higher than even 7.2? Transplanting? Adding lime? Spill it, lady. :grinning:

I just checked my journal. I used Florakleen, so I was able to use reduced water to flush.

As you can tell, I didn’t adjust my pH properly during the flush. I did get that ec down, though. PH & lockout issues can also come from hot soil. You did an initial flush before potting, though, right? How much water did you run through the soil?

Also, how far away are your lights? What are the temps in your tent (not climate of your area)?

Part of the issue is the soil. The problem with nute added soil is that every flush releases more nutes. So it’s going to be a lot of flushes before that happens. That’s why time release fertilizer soil isn’t recommended.


Transplant the plant into a soil that has no added nutrients. Even Miracle grow has a potting soil
That’s natural. Unless it’s an auto, you shouldn’t have any problems transplanting. You need a natural soil with no time released fertilizers @MeanieGreenie


My first few grows were nothing but problems with using hot soil, to start.

Florakleen became my friend. Moved to Promix. Still figuring things out, but so far, so good.

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Thanks everyone. My tent gets up to 44’C / 110’F during the day at the moment. I’m getting a bigger ventilation system to help keep the temp down. I did flush the soil for a couple of minutes about 4 times half an hour apart before planting to try wash out any nutrients built up but didn’t check soils PH. What’s the best way to bring tap water ph down?

You can purchase ph up & ph down for plants. In a pinch, you can use cider vinegar for ph down. But, since your soil is showing a ph of 6.2, you actually want to raise the ph.

Those temps are really probably part of the problem. After looking harder & re-reading your posts, I was also thinking possible led burn, and definite heat stress.

Yes @blackthumbbetty I think your right . With the PH being off, 110 temperature and the humidity being only 10 - 20 % . Intake fan but no exhaust fan ? . @MeanieGreenie Maybe you could raise your lights a little .

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Yeah. Not too much I can do about the temp but do you think an exhaust fan would be better. Suck the hottest air out instead? I’ll have to wait til I go to town to get ph up / down. My lights are 2 foot away from top of plants. Cause I’m skipping the veg stage, I have got 7 plants in the tent and only 4 are showing these symptoms. I’ll post some more photos when my lights come on in half an hour to show the others

Definitely an exhaust fan! Put it up high. Open ALL lower tent flaps. Keep a fan circulating air inside the tent (a clip fan or 2). With your arid environment, put up a wet towel inside the tent or use a humidifier outside the tent. Try to cool down the room your tent is in.

With those lights, start at 30 inches, minimum. Slowly lower them til you get to 24. Your tent is small, so you might not need both of those lights.

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I will change my intake to exhaust tonight. I have raised my lights to 30 inches. Cheers

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